What does the University of Michigan–led study published in Science conclude about how the strength and variability of El Niño–Southern Oscillation events over the past 40 years compare with those of the previous 1,000 years, how did researchers use 13 living and ancient Galápago

The study’s central conclusion is that ENSO’s warm-phase extremes have become unusually strong and variable: El Niño events over the past 40 years were about 36.5%—often rounded to nearly 40%—stronger than the average level reconstructed for the preceding millennium. The authors argue that the most likely main driver is anthropogenic warming, while stressing that individual El Niño events still arise from natural ocean–atmosphere variability. 1113

• How they reconstructed the past: The team combined 13 living and fossil Galápagos coral records into a monthly resolved, roughly 1,000-year eastern-tropical-Pacific temperature history. Coral Sr/Ca ratios serve principally as a temperature proxy; coral oxygen-isotope values contain temperature and seawater-composition signals. Using both allows a more robust reconstruction of monthly sea-surface-temperature swings associated with ENSO than either measurement alone. This matters because the Galápagos sits in a region that responds strongly to eastern-Pacific El Niño warming. 16

• What the record shows: Recent variability was not merely a warmer baseline ocean; the temperature excursions associated with ENSO were larger. In other words, the result concerns an intensification of the swings—especially El Niño heat anomalies—relative to the millennium-scale coral benchmark, not a claim that every present-day El Niño is necessarily stronger than every historical one. 1113

• Why the authors favor a human influence: They compared the coral reconstruction with simulations from 12 climate models and examined potential external natural drivers. The modeled and reconstructed timing/pattern did not support solar variability or volcanic eruptions as sufficient explanations for the recent rise; simulations incorporating human greenhouse-gas forcing were more consistent with the observed late-20th/early-21st-century intensification. That is attribution by converging evidence, not a literal proof that volcanic or solar effects played no role whatsoever. 1011

• Connection to the developing El Niño: The study is especially salient because NOAA’s August forecast put the chance of an October–December 2026 event exceeding every El Niño in the instrumental record since 1950 at 69%, using a Relative Oceanic Niño Index threshold of at least +2.5°C; later outlooks put the chance of a “very strong” event above 90%. 345 Reports of approximately 4°C warmer-than-normal waters refer to localized or regional anomalies and should not be conflated with NOAA’s basin-scale RONI threshold. A forecast does not validate the coral study by itself, but a record-scale event would be consistent with the study’s warning that a warmed climate can load the dice toward larger eastern-Pacific El Niño impacts. 34

Scientific reception and caution

• Supportive view: Kim Cobb, a coral-paleoclimate specialist whose earlier work established long coral-based ENSO records, has generally treated long, monthly resolved coral archives as crucial physical evidence for judging whether recent ENSO behavior exceeds natural variability. The new study’s unusually long Galápagos compilation therefore addresses a central limitation of relying only on the short instrumental record. 213

• Caution/skepticism: Michael Mann and other scientists view the result as physically plausible and broadly consistent with expectations that warming can amplify ENSO-related extremes, but this is not the same as claiming a settled consensus on every mechanism or on the precise 36.5% figure. Coral calibrations, site-specific signals, chronology, a 40-year comparison period, and differing model ENSO behavior all leave uncertainty; coral-proxy work can also produce substantial reconstruction error if treated as an exact thermometer. 4513 The strongest defensible reading is: the evidence supports a recent, unusual intensification with a substantial human contribution—not a guarantee that ENSO will strengthen monotonically in every future decade.

Practical implications

• Weather and climate risks: Strong El Niños reorganize atmospheric circulation globally, tending to raise global temperatures and shift storm tracks, rainfall, drought, flood, heat and wildfire risks. The exact regional outcome is event- and season-dependent, so it is not scientifically sound to attribute any single hurricane, flood, or drought solely to El Niño or solely to climate change. 1013

• Compound extremes: A more intense El Niño occurring on a warmer planet can magnify heat waves, marine heat waves, heavy rainfall and flood damage in some regions, while deepening heat and rainfall deficits elsewhere. Recent hurricane activity, exceptional rainfall and droughts should be understood as interacting risks: ENSO changes the circulation backdrop, while ocean warming and atmospheric moisture can increase the severity of some hazards. 1013

• Food, water and energy: The principal societal vulnerabilities are crop losses and food-price shocks from drought or flooding, altered fisheries and marine productivity, hydropower shortfalls where reservoirs depend on rainfall, and higher electricity demand during heat. These are exposure-and-preparedness problems as well as climate problems: early warning, water management, crop diversification and power-system resilience can reduce harm.

• Ecosystems and the scientific record: Extreme ocean heat causes coral bleaching and mortality. That threatens reefs and fisheries, but it also threatens the archive used in this research: living corals that record monthly chemistry may die before they can preserve future climate history. This makes protecting reefs, collecting and curating carefully permitted modern and fossil cores, and expanding records beyond a small number of sites scientifically important. 13

The study therefore strengthens the case for treating ENSO as a growing climate-risk multiplier rather than a purely natural, stationary cycle, while retaining appropriate uncertainty about the size and regional expression of future changes.